JP2009084440A - Ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition in which the occurrence of stickiness on the surface of a formed image is effectively suppressed while maintaining the curing sensitivity to the irradiation with a radiation, which hardly causes blocking even if the printed products after forming the images are superposed, and which has good jettability when applied to an inkjet device. <P>SOLUTION: The ink composition contains (a) a tertiary amine compound having a cationically polymerizable group, (b) a photo acid-generating agent and (c) a cationically polymerizable compound. Preferably, the tertiary amine compound (a) having the cationically polymerizable group has a hindered amine structure as the tertiary amine structure and is a compound having a vinyl ether group, an epoxy group or an oxetane group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink composition. Specifically, the present invention relates to an ink composition that can be cured with high sensitivity to radiation and can form an image having no stickiness on the surface, and is suitable for ink jet recording.

  As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. Among these, the ink jet method can be implemented with an inexpensive apparatus, and the ink can be efficiently used because the ink is ejected only on the required image portion to directly form the image on the recording medium. Running cost is low. Furthermore, there is little noise and it is excellent as an image recording method.

According to the inkjet system, printing is possible not only on plain paper but also on non-water-absorbing recording media such as plastic sheets and metal plates. However, high speed and high image quality are important issues for printing. The time required for drying and curing the droplets after printing has a property of greatly affecting the productivity of printed matter and the sharpness of the printed image.
As one of the ink jet methods, there is a recording method using an ink for ink jet recording that can be cured by irradiation of radiation. According to this method, the productivity of printing can be improved and a sharp image can be formed by irradiating with radiation immediately after printing or after a certain time and curing the ink droplets.
By achieving high sensitivity of ink for ink jet recording that can be cured by irradiation with radiation such as ultraviolet rays, high curability is imparted to radiation, improving productivity of ink jet recording, reducing power consumption, and applying to radiation generators. There are many benefits such as longer life by reducing the load and prevention of volatilization of low molecular weight materials due to insufficient curing. In addition, high sensitivity improves the strength of the image formed by the ink for ink jet recording in particular, and particularly when applied to the formation of a lithographic printing plate, the curing strength of the image area is increased, resulting in high printing durability. Will be obtained.

  Such a curable ink jet method using radiation, for example, ultraviolet rays has been attracting attention in recent years because it has a relatively low odor, and can be recorded on a recording medium having no quick drying and no ink absorption. An ultraviolet ray curable ink composition for inkjet use is disclosed. Although these radical polymerization inks are excellent in curing speed and can form images without bleeding, there is a problem in that the adhesion to a recording medium is reduced due to volume shrinkage during curing.

For this reason, for the purpose of improving the adhesion to the recording medium, a cationic polymerization type ink composition having a small shrinkage rate at the time of ultraviolet curing has been proposed (for example, see Patent Document 1). However, these cationic polymerization type inks are not sufficiently stable at the time of storage due to the reaction based on the acid generated with the passage of time, which has been a major obstacle to practical use. For this reason, as an attempt to improve storage stability, a technique of adding a basic compound or a thermal base generator has been proposed (for example, see Patent Documents 2 to 4), but the basic compound is generated by exposure. It has been found that a new problem arises that the curing sensitivity of the ink is lowered due to the inhibition of the function of the acid.
In the case of a cationic polymerization type ink, if a low molecular weight basic compound as a stabilizer remains unreacted even after image formation, it will leach on the image surface and cause stickiness of the image surface, thus improving tack sensitivity. It is anxious that.
Japanese Patent Laid-Open No. 9-183928 JP 2003-312121 A JP 2003-341217 A JP 2004-91558 A

  The object of the present invention made in consideration of the above problems is to prevent the occurrence of stickiness on the formed image surface while maintaining the curing sensitivity to radiation irradiation, and even when the printed matter after image formation is laminated. An object of the present invention is to provide an ink composition which does not cause blocking and has good dischargeability when applied to an ink jet apparatus.

Means for solving the above-mentioned problems are as follows.
<1> An ink composition comprising (a) a tertiary amine compound having a cationic polymerizable group, (b) a photoacid generator, and (c) a cationic polymerizable compound.
<2> The ink composition according to <1>, wherein the tertiary amine structure in the tertiary amine compound (a) having a cationic polymerizable group is a hindered amine structure.
<3> The ink composition according to <1> or <2>, wherein the tertiary amine compound (a) having a cationic polymerizable group has a vinyl ether group. <4> The (a) cationic polymerizable property The ink composition according to <1> or <2>, wherein the tertiary amine compound having a group has an epoxy group or an oxetane group.
<5> The ink composition according to any one of <1> to <4>, further comprising (D) a colorant.
<6> The ink composition according to any one of <1> to <5>, which is for inkjet.

The ink composition of the present invention can be used for normal printing to form an image with high image quality and excellent strength, and not only a high-quality printed matter can be obtained, but also suitable for the production of resists, color filters, and optical discs. It can be used and is also useful as an optical modeling material.
Further, by applying the ink jet recording method, an image area that is hardened with high sensitivity and does not stick to the surface can be directly formed on a non-absorbable recording medium based on digital data. Even when the printed matter formed using the ink composition is laminated after printing, blocking due to stickiness of the ink image is suppressed.

  According to the present invention, the occurrence of stickiness of the formed image surface is effectively suppressed while maintaining the curing sensitivity to radiation irradiation, and no blocking occurs even when the printed materials after image formation are laminated, and the inkjet apparatus Thus, it is possible to provide an ink composition having good ejection properties when applied to the ink.

[Ink composition]
The ink composition of the present invention comprises (a) a tertiary amine compound having a cationic polymerizable group, (b) a photoacid generator, and (c) a cationic polymerizable compound. If desired, it may further contain (d) a colorant.

  The term “radiation” as used in the present invention is not particularly limited as long as it is actinic radiation that can impart energy capable of generating an initiation species in the ink composition by irradiation, and is broadly α-ray, γ-ray, X Actinic radiation including rays, ultraviolet rays, visible rays, electron beams and the like. Among these, ultraviolet rays and electron beams are preferable from the viewpoint of curing sensitivity and device availability, and ultraviolet rays are particularly preferable. Therefore, the ink composition of the present invention is an ink composition that can be cured by irradiating ultraviolet rays as radiation. It is preferable that it is a thing.

Radiation curable cationic polymerization ink compositions such as ultraviolet rays are superior to radical polymerization ink compositions in terms of film properties and sensitivity, but they are not subject to polymerization inhibition by oxygen, so they are resistant to heat and light. Stability is a problem.
In the ink composition of the present invention, the basic compound as a stabilizer has a polymerizable group, so that it is quickly cured without impairing sensitivity, and the basic compound is imaged due to the polymerizable group. Since the low molecular weight basic compound is not leached on the image surface, the stickiness of the surface is effectively suppressed, the tack sensitivity is improved, and the ink composition of the present invention is used. Even if the formed printed matter is stacked, the occurrence of blocking due to stickiness of the ink image can be suppressed.
Although the mechanism of action that exerts such an effect has not been clarified in detail, (a) due to the amine structure in the tertiary amine compound having a cationically polymerizable group, when the exposure is not performed, the amine The structure effectively traps a small amount of undesired acid generated from the photoacid generator (b) to suppress the curing reaction, and when sufficient exposure is performed, the tertiary amine compound Due to the cationically polymerizable group in the ink, it is cured with an acid together with the adjacent (c) cationically polymerizable compound, and is fixed in the image portion formed by curing the ink without causing bleeding to the surface. It is considered that the occurrence of surface stickiness caused by the leaching of the low molecular weight tertiary amine compound is effectively suppressed.
Hereinafter, each component used in the ink composition of the present invention will be described in order.

[(A) Tertiary amine compound having cationically polymerizable group]
Next, (a) a tertiary amine compound having a cationic polymerizable group (hereinafter, appropriately referred to as “polymerizable amine compound”), which is a characteristic component used in the present invention, will be described.

The (a) polymerizable amine compound in the present invention is not particularly limited as long as it is a tertiary amine compound having at least one cationic polymerizable group in the molecule, and there is only one tertiary amine structure in the molecule. There may be more than one. The number of tertiary amine structures in one molecule is preferably 1 to 4 and more preferably 1 to 3 from the viewpoints of suppressing an increase in initial viscosity and suppressing yellowing.
Although the form of the tertiary amine structure is arbitrary, the use of a so-called hindered amine compound having a basic nitrogen atom having a large steric hindrance traps a small amount of acid generated without inhibiting the growth reaction of cationic polymerization. It is preferable from the viewpoint of maintaining high sensitivity and improving stability over time.

  Examples of such a hindered amine structure include those in which basic nitrogen has sufficient steric hindrance to lower the reactivity with the cation end. There are many molecules around the basic nitrogen atom. For example, having a bulky substituent causes steric hindrance, and the factor that inhibits the cationic polymerization reaction as a basic compound is reduced. Tertiary amines are particularly preferred. In general, when sufficient steric hindrance cannot be obtained, the degree of polymerization of the polymer produced in the cured film is reduced by chain transfer in the system, which is thought to lead to a decrease in sensitivity. Since such an amine compound itself has cationic polymerizability, there is no concern about chain transfer, etc., and it contributes to the curing reaction together with the adjacent cationic polymerizable compound by applying energy, so that it is a preferable embodiment from the viewpoint of sensitivity. Can do.

  By adopting such a hindered amine structure, while maintaining the trap function of an undesired trace amount of acid generated by heat or light, it is different from a conventionally used basic compound when cured by normal exposure. It is considered that the steric hindrance does not inhibit the growth reaction of the cation end during the cationic polymerization reaction by the basic site, so that the progress of the polymerization is not suppressed and the sensitivity is not lowered.

  (A) Preferable examples of the tertiary amine structure in the polymerizable amine compound include structures represented by any one of the following general formulas I to VII.

R ¹ represents a branched alkyl group having 3 to 8 carbon atoms (eg, isopropyl, isobutyl, tert-butyl, isopentyl, etc.), a cyclic alkyl group having 3 to 10 carbon atoms (eg, cyclopentyl, cyclohexyl, etc.), or a carbon number Represents 7 to 20 aralkyl groups. R ² represents a linear alkyl group having 1 to 4 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. R ³ is a hydrogen atom, a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group having 3 to 6 carbon atoms, a cyclic alkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or 7 carbon atoms. To an aralkyl group having from 20 to 20 or an alkenyl group having from 2 to 20 carbon atoms.
Here, a plurality of R ¹ and R ² present in one molecule may be the same or different from each other, and may be bonded to each other to form a ring structure. Z represents a divalent organic group made of hydrocarbon. n and m represent an integer of 1 to 3.
More preferably, it is a hindered amine structure having an alkyl-substituted structure represented by the above general formula I and general formula IV.

Further, (a) at least one cationic polymerizable group in the polymerizable amine compound may be present in one molecule, and two or more cationic polymerizable groups may be present. The plurality of cationic polymerizable groups may be of the same type, or may be mixed with different polymerizable groups. The number of cationically polymerizable groups in one molecule is preferably 1 to 4 and more preferably 1 to 3 from the viewpoint of suppressing an increase in initial viscosity.
The type of the cationic polymerizable group is not particularly limited, and any cationic polymerizable group that can be cured by an acid can be used. Examples thereof include a substituent having a conjugated double bond, an oxetane ring, and an epoxy ring. The substituent which has is mentioned.
Among these, a substituent selected from a vinyl ether group, an alicyclic epoxide, and an oxetane group is particularly preferable from the viewpoint of copolymerization reactivity with a cationically polymerizable monomer in the ink and synthesis suitability.

The bonding mode between the tertiary amine structure and the cationic polymerizable group is also arbitrary. For example, the mode in which cationic polymerization is bonded to the nitrogen atom constituting the ring in the cyclic amine structure, or the ring in the cyclic amine structure. One or more cationically polymerizable groups may be bonded to the amine structure, such as an embodiment where cationically polymerizable is bonded to an arbitrary position of the carbon atom to be bonded, and 1 is bonded to the carbon atom constituting the epoxy ring or oxetane ring. One or more tertiary amine structures may be bonded to one cationically polymerizable group, such as an embodiment in which two or more tertiary amine structures are present.
Further, the tertiary amine structure and the cationic polymerizable group may be directly bonded or may be bonded via an appropriate linking group. Suitable linking groups include a straight-chain alkylene group having 1 to 10 carbon atoms, a branched alkylene group, an alkyleneoxy group having 1 to 8 carbon atoms, and an aralkyl having 1 to 12 carbon atoms, which may have a hetero atom as a substituent. Group, and the like. More preferably, an alkylene group having 1 to 6 carbon atoms is used.

  Specific examples of the polymerizable amine compound (a) are exemplified compounds (A-1) to (A-33), but the present invention is not limited thereto.

Among these, A-1, A-3, A-4, A-6, A-11, A-24, and A-26 are preferable from the viewpoint of performance and synthesis suitability.
In the ink composition of the present invention, (a) the polymerizable amine compound may be used alone or in combination of two or more.

  The content of the polymerizable amine compound (a) in the ink composition of the present invention is such that both curing sensitivity maintenance and storage stability are compatible, ejection stability when applied to an ink jet apparatus, and surface stickiness of the formed image. From the viewpoint of suppressing yellowing, it is preferably from 0.01% by mass to 25% by mass, more preferably from 0.1% by mass to 20% by mass, in terms of solid content in the ink composition, from 1% by mass to 15% by mass is particularly preferred.

[(B) Photoacid generator]
In the ink composition of the present invention, a compound capable of generating a polymerization initiation species of the ink composition and generating an acid upon irradiation with radiation, that is, a photoacid generator is used.
Examples of photoacid generators that can be used in the present invention include photoinitiators for photocationic polymerization, photoinitiators for photoradical polymerization, photodecolorants for dyes, photochromic agents, and light used for microresists. (400-200 nm ultraviolet rays, far ultraviolet rays, particularly preferably g-line, h-line, i-line, KrF excimer laser beam), ArF excimer laser beam, electron beam, X-ray, molecular beam, ion beam, etc. A compound capable of generating can be appropriately selected and used.

  Examples of such a photoacid generator include an onium salt compound such as a diazonium salt, a phosphonium salt, a sulfonium salt, and an iodonium salt that decomposes upon irradiation with radiation, an imide sulfonate, an oxime sulfonate, a diazodisulfone, a disulfone, Examples thereof include sulfonate compounds such as o-nitrobenzyl sulfonate.

  Other compounds that generate an acid upon irradiation with actinic rays or radiation used in the present invention include, for example, S.P. I. Schlesinger, Photogr. Sci. Eng. 18, 387 (1974), T .; S. Diazonium salts described in Bal etal, Polymer, 21, 423 (1980), U.S. Pat. Nos. 4,069,055, 4,069,056, Re 27,992, JP-A-3-140140, etc. An ammonium salt according to claim 1, C. Necker et al., Macromolecules, 17, 2468 (1984), C.I. S. Wen et al, Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988), U.S. Pat. Nos. 4,069,055, 4,069,056, and the like; V. Crivello et al, Macromolecules, 10 (6), 1307 (1977), Chem. & Eng. News, Nov. 28, p31 (1988), European Patent Nos. 104,143, 339,049, 410,201, JP-A-2-150848, JP-A-2-296514 and the like,

  J. et al. V. Crivello et al, Polymer J. et al. 17, 73 (1985), J. Am. V. Crivello et al. J. et al. Org. Chem. 43, 3055 (1978); R. Watt et al. PolymerSci. , Polymer Chem. Ed. , 22, 1789 (1984), J. Am. V. Crivello et al., Polymer Bull. 14, 279 (1985), J. Am. V. Crivello et al, Macromolecules, 14 (5), 1141 (1981), J. MoI. V. Crivello et al. Polymer Sci. , Polymer Chem. Ed. 17, 2877 (1979), European Patent Nos. 370,693, 161,811, 410,201, 339,049, 233,567, 297,443, and 297,442. U.S. Pat.Nos. 3,902,114, 4,933,377, 4,760,013, 4,734,444, 2,833,827, German Patent 2, Nos. 904, 626, 3,604, 580, 3,604, 581, JP-A-7-28237, 8-27102 and the like,

  J. et al. V. Crivello et al., Macromolecules, 10 (6), 1307 (1977), J. MoI. V. Crivello et al. Polymer Sci. , Polymer Chem. Ed. , 17, 1047 (1979), etc., selenonium salts, C.I. S. Wen et al, Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988) and other onium salts such as arsonium salts, U.S. Pat. -32070, JP-A-60-239736, JP-A-61-169835, JP-A-61-169837, JP-A-62-58241, JP-A-62-212401, JP-A-63-70243 , Organic halogen compounds described in JP-A-63-298339 and the like; Meier et al, J.A. Rad. Curing, 13 (4), 26 (1986), T.A. P. Gill et al, Inorg. Chem. , 19, 3007 (1980), D.M. Astruc, Acc. Chem. Res. , 19 (12), 377 (1986), and organometallic / organic halides described in JP-A-2-161445, etc.

  S. Hayase et al. Polymer Sci. 25, 753 (1987), E.I. Reichmanis et al. Polymer Sci. , Polymer Chem. Ed. , 23, 1 (1985), Q.M. Q. Zhu etal, J. et al. Photochem. 36, 85, 39, 317 (1987), B.R. Amit etal, Tetrahedron Lett. , (24) 2205 (1973), D.M. H. R. Barton et al. Chem. Soc. , 3571 (1965), p. M.M. Collins et al, J.A. Chem. Soc. Perkin I, 1695 (1975), M .; Rudinstein et al., Tetrahedron Lett. , (17), 1445 (1975), J. MoI. W. Walker et al. Am. Chem. Soc. 110, 7170 (1988), S.A. C. Busman et al. Imaging Technol. 11 (4), 191 (1985), H. et al. M.M. Houlihan et al, Macormolecules, 21, 2001 (1988), p. M.M. Collins et al. Chem. Soc. , Chem. Commun. 532 (1972), S.A. Hayase et al., Macromolecules, 18, 1799 (1985), E.I. Reichmanis et al. Electrochem. Soc. , Solid State Sci. Technol. , 130 (6), F.M. M.M. Houlihan et al, Macromolecules, 21, 2001 (1988), European Patent Nos. 0290,750, 046,083, 156,535, 271,851, 0,388,343, US Patent No. 3 , 901,710, 4,181,531, JP-A-60-198538, JP-A-53-133022 and the like, a photoacid generator having an o-nitrobenzyl type protecting group,

  M.M. TUNOOKA et al, Polymer Preprints Japan, 35 (8), G.M. Berner et al. Rad. Curing, 13 (4), W.M. J. et al. Mijs et al, Coating Technol. , 55 (697), 45 (1983), Akzo, H .; Adachi et al, Polymer Preprints, Japan, 37 (3), European Patent No. 0199,672, No. 84515, No. 044,115, No. 618,564, No. 0101,122, US Pat. No. 4,371 , 605, 4,431,774, JP-A 64-18143, JP-A-2-245756, JP-A-3-140109, etc. Compounds generating an acid, disulfone compounds described in JP-A-61-1166544 and JP-A-2-71270, diazo compounds described in JP-A-3-103854, JP-A-3-103856, and JP-A-4-210960 Examples thereof include ketosulfone and diazodisulfone compounds.

  Further, a group which generates an acid by these light, or a compound in which a compound is introduced into the main chain or side chain of the polymer, for example, M.I. E. Woodhouse et al., J. MoI. Am. Chem. Soc. 104, 5586 (1982), S .; P. Pappas et al. Imaging Sci. , 30 (5), 218 (1986), S .; Kondo et al, Makromol. Chem. , Rapid Commun. , 9, 625 (1988), Y. et al. Yamada et al, Makromol. Chem. 152, 153, 163 (1972), J. Am. V. Crivello et al, J.A. PolymerSci. , Polymer Chem. Ed. 17, 3845 (1979), U.S. Pat. No. 3,849,137, German Patent No. 3,914,407, JP-A 63-26653, JP-A 55-164824, JP-A 62- 69263, JP-A 63-146038, JP-A 63-163452, JP-A 62-153853, JP-A 63-146029, and the like can be used. For example, diazonium salts, ammonium salts, phosphonium salts, iodonium salts, sulfonium salts, selenonium salts, onium salts such as arsonium salts, organic halogen compounds, organic metal / organic halides, photoacid generators having o-nitrobenzyl type protecting groups Examples thereof include a compound capable of generating a sulfonic acid by photolysis represented by an agent, iminosulfonate, and the like, a disulfone compound, a diazoketosulfone, and a diazodisulfone compound.

  Furthermore, V. N. R. Pillai, Synthesis, (1), 1 (1980), A.M. Abad et al., Tetrahedron Lett. , (47) 4555 (1971), D.M. H. R. Barton et al, J.A. Chem. Soc. , (C), 329 (1970), U.S. Pat. No. 3,779,778, European Patent No. 126,712, and the like, compounds that generate an acid by light can also be used.

  Preferred examples of the photoacid generator that can be used in the present invention include compounds represented by the following formulas (b1), (b2), and (b3).

In formula (b1), R ²⁰¹ , R ²⁰² and R ²⁰³ each independently represents an organic group.
X ⁻ represents a non-nucleophilic anion, preferably a sulfonate anion, a carboxylate anion, a bis (alkylsulfonyl) amide anion, a tris (alkylsulfonyl) methide anion, BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ or the following The organic anion which has a carbon atom is preferable.

  Preferable organic anions include organic anions represented by the following formula.

Rc ¹ represents an organic group.
Examples of the organic group in Rc ¹ include those having 1 to 30 carbon atoms, and preferably an alkyl group, a cycloalkyl group, an aryl group, or a plurality of these are a single bond, —O—, —CO ₂ —, —S—. , —SO ₃ —, —SO ₂ N (Rd ¹ ) — and the like.

Rd ¹ represents a hydrogen atom or an alkyl group.
Rc ³ , Rc ⁴ and Rc ⁵ each independently represents an organic group.
Preferred examples of the organic group for Rc ³ , Rc ⁴ , and Rc ⁵ include the same organic groups as those for Rc ¹ , and most preferred is a perfluoroalkyl group having 1 to 4 carbon atoms.
Rc ³ and Rc ⁴ may be bonded to form a ring.
Examples of the group formed by combining Rc ³ and Rc ⁴ include an alkylene group and an arylene group. Preferably, it is a C2-C4 perfluoroalkylene group.

As the organic groups of Rc ¹ and Rc ^{3 to} Rc ⁵ , the most preferable one is an alkyl group substituted at the 1-position with a fluorine atom or a fluoroalkyl group, or a phenyl group substituted with a fluorine atom or a fluoroalkyl group. By having a fluorine atom or a fluoroalkyl group, the acidity of the acid generated by light irradiation is increased and the sensitivity is improved.

The carbon number of the organic group as R ²⁰¹ , R ²⁰² and R ²⁰³ is generally 1 to 30, preferably 1 to 20.
Two of R ^{201 to} R ²⁰³ may be bonded to form a ring structure, and the ring may contain an oxygen atom, a sulfur atom, an ester bond, an amide bond, or a carbonyl group. Examples of the group formed by combining two of R ^{201 to} R ²⁰³ include an alkylene group (eg, butylene group, pentylene group).

Specific examples of the organic group as R ²⁰¹ , R ²⁰² and R ²⁰³ include corresponding groups in the compounds (b1-1), (b1-2) and (b1-3) described later.

In addition, the compound which has two or more structures represented by Formula (b1) may be sufficient. For example, at least one of R ^{201 to} R ²⁰³ of the compound represented by the general formula (b1) is directly or linked to at least one of R ^{201 to} R ²⁰³ in the other compound represented by the formula (b1). It may be a compound having a structure bonded through a group.

  Further preferred examples of the component (b1) include compounds (b1-1), (b1-2), and (b1-3) described below.

Compound (b1-1) is in which at least one aryl group ^R 201 ^{to R 203} in formula (b1), arylsulfonium compound, i.e., a compound having arylsulfonium as a cation.

In the arylsulfonium compound, all of R ^{201 to} R ²⁰³ may be an aryl group, or a part of R ^{201 to} R ²⁰³ may be an aryl group, and the rest may be an alkyl group or a cycloalkyl group.

  Examples of the arylsulfonium compound include triarylsulfonium compounds, diarylalkylsulfonium compounds, aryldialkylsulfonium compounds, diarylcycloalkylsulfonium compounds, aryldicycloalkylsulfonium compounds, and the like.

  The aryl group of the arylsulfonium compound is preferably an aryl group such as a phenyl group or a naphthyl group, or a heteroaryl group such as an indole residue or a pyrrole residue, more preferably a phenyl group or an indole residue. When the arylsulfonium compound has two or more aryl groups, the two or more aryl groups may be the same or different.

As the alkyl group that the arylsulfonium compound has as necessary, a linear or branched alkyl group having 1 to 15 carbon atoms is preferable. For example, a methyl group, an ethyl group, a propyl group, an n-butyl group, sec -A butyl group, a t-butyl group, etc. can be mentioned.
The cycloalkyl group that the arylsulfonium compound has as necessary is preferably a cycloalkyl group having 3 to 15 carbon atoms, and examples thereof include a cyclopropyl group, a cyclobutyl group, and a cyclohexyl group.

The aryl group, alkyl group and cycloalkyl group of R ^{201 to} R ²⁰³ are an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (for example, 6 to 14 carbon atoms). , An alkoxy group (for example, having 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, or a phenylthio group may be substituted. Preferred substituents are linear or branched alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 3 to 12 carbon atoms, and linear, branched or cyclic alkoxy groups having 1 to 12 carbon atoms, and most preferred. Is an alkyl group having 1 to 4 carbon atoms and an alkoxy group having 1 to 4 carbon atoms. The substituent may be substituted with any one of the three R ^{201 to} R ²⁰³ , or may be substituted with all three. When R ^{201 to} R ²⁰³ are an aryl group, the substituent is preferably substituted at the p-position of the aryl group.

Next, the compound (b1-2) will be described.
The compound (b1-2) is a compound when R ^{201 to} R ²⁰³ in the formula (b1) each independently represents an organic group that does not contain an aromatic ring. Here, the aromatic ring includes an aromatic ring containing a hetero atom.
The organic group not containing an aromatic ring as R ^{201 to} R ²⁰³ generally has 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms.
R ^{201 to} R ²⁰³ are each independently preferably an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably a linear, branched, cyclic 2-oxoalkyl group, or an alkoxycarbonylmethyl group, particularly preferably Is a linear, branched 2-oxoalkyl group.

The alkyl group as R ^{201 to} R ²⁰³ may be either linear or branched, and is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group). Group, a butyl group, a pentyl group), and a linear, branched 2-oxoalkyl group, and an alkoxycarbonylmethyl group are more preferable.

The cycloalkyl group as R ^{201 to} R ²⁰³ preferably includes a cycloalkyl group having 3 to 10 carbon atoms (cyclopentyl group, cyclohexyl group, norbornyl group), and a cyclic 2-oxoalkyl group is more preferable.

Preferred examples of the linear, branched and cyclic 2-oxoalkyl group represented by R ^{201 to} R ²⁰³ include a group having> C═O at the 2-position of the above alkyl group or cycloalkyl group.
The alkoxy group in the alkoxycarbonylmethyl group as R ^{201 to} R ²⁰³ is preferably an alkoxy group having 1 to 5 carbon atoms (methoxy group, ethoxy group, propoxy group, butoxy group, pentoxy group).
R ^{201 to} R ²⁰³ may be further substituted with a halogen atom, an alkoxy group (eg, having 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

  The compound (b1-3) is a compound represented by the following formula (b1-3) and is a compound having a phenacylsulfonium salt structure.

In formula (b1-3), R ^{1c to} R ^5c each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, or a halogen atom.
R ^6c and R ^7c each independently represents a hydrogen atom, an alkyl group or a cycloalkyl group.
R ^x and R ^y each independently represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group.
Any two or more of R ^{1c to} R ^5c , R ^6c and R ^7c , and R ^x and R ^y may be bonded to each other to form a ring structure.
Zc ^- represents a non-nucleophilic anion, in X in Formula (b1) ^- may be the same as the non-nucleophilic anion.

The alkyl group as R ^{1c to} R ^7c may be either linear or branched, and for example, a linear and branched alkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms (for example, Methyl group, ethyl group, linear or branched propyl group, linear or branched butyl group, linear or branched pentyl group).

Preferred examples of the cycloalkyl group represented by R ^{1c to} R ^7c include cycloalkyl groups having 3 to 8 carbon atoms (for example, a cyclopentyl group and a cyclohexyl group).

The alkoxy group as R ^{1c to} R ^{5c may} be linear, branched or cyclic, for example, an alkoxy group having 1 to 10 carbon atoms, preferably a linear or branched alkoxy group having 1 to 5 carbon atoms. (For example, methoxy group, ethoxy group, linear or branched propoxy group, linear or branched butoxy group, linear or branched pentoxy group), C3-C8 cyclic alkoxy group (for example, cyclopentyloxy group, cyclohexyloxy group) ).

Examples of the group formed by combining any two or more of R ^{1c to} R ^5c , R ^6c and R ^7c , and R ^x and R ^y include a butylene group and a pentylene group. This ring structure may contain an oxygen atom, a sulfur atom, an ester bond, or an amide bond.

Preferably, any one of R ^{1c to} R ^5c is a linear or branched alkyl group, a cycloalkyl group, or a linear, branched, or cyclic alkoxy group, and more preferably the sum of the carbon number of R ^1c to R ^5c is 2-15. Solvent solubility is further improved, and generation of particles during storage is suppressed, which is preferable.

^Examples of the alkyl group and cycloalkyl group as R ^x and R ^y include the same alkyl groups and cycloalkyl groups as R ^{1c to} R ^7c .
R ^x and R ^y are preferably a 2-oxoalkyl group or an alkoxycarbonylmethyl group.
Examples of the 2-oxoalkyl group include a group having> C═O at the 2-position of the alkyl group or cycloalkyl group as R ^{1c to} R ^5c .
The alkoxy group in the alkoxycarbonylmethyl group may be the same as the alkoxy group as R ^1c to R ^5c.

R ^x and R ^y are preferably an alkyl group or cycloalkyl group having 4 or more carbon atoms, more preferably 6 or more, and still more preferably 8 or more alkyl groups or cycloalkyl groups.

In formulas (b2) and (b3), R ^{204 to} R ²⁰⁷ each independently represents an aryl group, an alkyl group, or a cycloalkyl group. X ⁻ represents a non-nucleophilic anion, and examples thereof include the same non-nucleophilic anion as X ^{− in} formula (b1).

The aryl group for R ^{204 to} R ²⁰⁷ is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.
The alkyl group as R ^{204 to} R ²⁰⁷ may be either linear or branched, and is preferably a linear or branched alkyl group having 1 to 10 carbon atoms (for example, methyl group, ethyl group, propyl group). Group, butyl group, pentyl group). The cycloalkyl group as R ²⁰⁴ to R ²⁰⁷ is preferably, and a cycloalkyl group having 3 to 10 carbon atoms (e.g., cyclopentyl, cyclohexyl, norbornyl).
The R ²⁰⁴ to R ²⁰⁷ are substituents which may have, for example, an alkyl group (for example, 1 to 15 carbon atoms), a cycloalkyl group (for example, 3 to 15 carbon atoms), an aryl group (e.g., 6 carbon atoms 15), alkoxy groups (for example, having 1 to 15 carbon atoms), halogen atoms, hydroxyl groups, phenylthio groups and the like.

  Examples of the compound that generates an acid upon irradiation with actinic rays or radiation that may be used further include compounds represented by the following formulas (b4), (b5), and (b6).

In formulas (b4) to (b6), Ar ³ and Ar ⁴ each independently represent an aryl group.
R ²⁰⁶ , R ²⁰⁷ and R ²⁰⁸ each independently represents an alkyl group, a cycloalkyl group or an aryl group.
A represents an alkylene group, an alkenylene group or an arylene group.

  Preferable examples of the photoacid generator include compounds represented by formulas (b1) to (b3).

  Preferred examples of the (B) cationic polymerization initiator [(b-1) to (b-96)] that can be used in the present invention are listed below, but the present invention is not limited thereto.

Examples of the photoacid generator that can be used as a cationic polymerization initiator in the present invention include the oxazole derivatives described in JP-A-2002-122994, paragraphs [0029] to [0030], in addition to the compound group described above, An s-triazine derivative or the like is also preferably used.
Onium salt compounds and sulfonate compounds exemplified in JP-A-2002-122994, paragraphs [0037] to [0063] can also be suitably used as the photoacid generator.

In the ink composition of the present invention, (b) the cationic polymerization initiator may be used alone or in combination of two or more.
The content of the cationic polymerization initiator (b) in the ink composition is preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass in terms of the total solid content of the ink composition. It is 1 mass%, More preferably, it is 1 mass%-7 mass%.
Here, the solid content in the ink composition in the present invention is a component obtained by removing volatile components such as a solvent described later from the ink composition.

[(C) Cationic polymerizable compound]
The (c) cationic polymerizable compound used in the present invention is not particularly limited as long as it is a compound that causes a polymerization reaction by an acid generated from the (b) cationic polymerization initiator (photoacid generator) and cures. Various known cationic polymerizable monomers known as photo cationic polymerizable monomers can be used. Examples of the cationic polymerizable monomer include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and 2001-2001. Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in each publication such as No. 220526.

  Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, aromatic epoxides, etc. The aromatic epoxide includes, for example, a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin. Di- or polyglycidyl ether produced by reaction, for example, di- or polyglycidyl ether of bisphenol A or its alkylene oxide adduct, di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, and novolak Type epoxy resin and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is mentioned preferably.
Examples of the aliphatic epoxide include dihydric polyhydridyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or 1,6. -Diglycidyl ether of alkylene glycol such as diglycidyl ether of hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its adduct of alkylene oxide Polyalkylene glycol diglycol represented by diglycidyl ether of ether, polypropylene glycol or its alkylene oxide adduct Jill ether, and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Examples of monofunctional epoxy compounds that can be used in the present invention include, for example, phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, 1,2-butylene oxide, 1,3-butadiene monooxide, 1,2-epoxydodecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3 -Vinylcyclohexene oxide etc. are mentioned.

  Examples of polyfunctional epoxy compounds include, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, and brominated bisphenol. S diglycidyl ether, epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxy 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxy Hexylmethyl) adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ', 4'-epoxy- 6'-methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, ethylene glycol di (3,4-epoxycyclohexylmethyl) ether, ethylenebis (3,4-epoxycyclohexanecarboxylate) ), Dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl Ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8 -Diepoxyoctane, 1,2,5,6-diepoxycyclooctane and the like.

  Among these epoxy compounds, aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and alicyclic epoxides are particularly preferable.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylol. Di- or trivinyl ether compounds such as propane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-pro Vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Specifically, examples of monofunctional vinyl ethers include, for example, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, Cyclohexylmethyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether , Methoxypolyethyleneglycol Ruvinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, Examples include chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, and the like.

Examples of the polyfunctional vinyl ether include, for example, ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, and bisphenol F. Divinyl ethers such as alkylene oxide divinyl ether; trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol Hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether, propylene oxide addition Examples thereof include polyfunctional vinyl ethers such as pentaerythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.
As the vinyl ether compound, a di- or trivinyl ether compound is preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and a divinyl ether compound is particularly preferable.

The oxetane compound in the present invention refers to a compound having an oxetane ring, and a known oxetane compound is arbitrarily selected as described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217. Can be used.
The compound having an oxetane ring that can be used in the ink composition of the present invention is preferably a compound having 1 to 4 oxetane rings in the structure. By using such a compound, it becomes easy to maintain the viscosity of the ink composition in a good handling property range, and it is possible to obtain high adhesion of the cured ink to the recording medium. .

  Examples of the compound having 1 to 2 oxetane rings in the molecule include compounds represented by the following formulas (1) to (3).

R ^a1 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group, or a thienyl group. When two R ^a1 are present in the molecule, they may be the same or different.
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Preferred examples of the fluoroalkyl group include those in which any hydrogen of these alkyl groups is substituted with a fluorine atom.
R ^a2 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms, or 2 to 6 carbon atoms. Represents an alkoxycarbonyl group, and an N-alkylcarbamoyl group having 2 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkenyl group include a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, and 2-methyl-2. -Propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group and the like. Examples of the group having an aromatic ring include phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group and the like. Can be mentioned. As the alkylcarbonyl group, an ethylcarbonyl group, a propylcarbonyl group, a butylcarbonyl group, etc., as an alkoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, etc., as an N-alkylcarbamoyl group, Examples thereof include an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group, and a pentylcarbamoyl group.

R ^a3 represents a linear or branched alkylene group, a linear or branched poly (alkyleneoxy) group, a linear or branched unsaturated hydrocarbon group, an alkylene group containing a carbonyl group or a carbonyl group, a carboxyl group Represents an alkylene group containing, an alkylene group containing a carbamoyl group, or a group shown below. Examples of the alkylene group include an ethylene group, a propylene group, and a butylene group. Examples of the poly (alkyleneoxy) group include a poly (ethyleneoxy) group and a poly (propyleneoxy) group. Examples of the unsaturated hydrocarbon group include a propenylene group, a methylpropenylene group, and a butenylene group.

When R ^a3 is the above polyvalent group, R ^a4 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a cyano group, a mercapto group, A lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group is represented.
R ^a5 represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .
R ^a6 represents an alkyl group having 1 to 4 carbon atoms or an aryl group, and n is an integer of 0 to 2,000. R ^a7 represents an alkyl group having 1 to 4 carbon atoms, an aryl group, or a monovalent group having the following structure. In the following formula, R ^a8 is an alkyl group having 1 to 4 carbon atoms or an aryl group, and m is an integer of 0 to 100.

  Examples of the compound having 3 to 4 oxetane rings include a compound represented by the following formula (4).

In Formula (4), R ^a1 has the same ^meaning as in Formula (1). In addition, examples of R ^a9 that is a polyvalent linking group include branched alkylene groups having 1 to 12 carbon atoms such as groups represented by A to C below, and branched poly ( An alkyleneoxy) group or a branched polysiloxy group such as a group represented by E below. j is 3 or 4.

In the above A, R ^a10 represents a methyl group, an ethyl group, or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Another embodiment of the oxetane compound that can be suitably used in the present invention includes a compound represented by the following formula (5) having an oxetane ring in the side chain.

In the formula (5), R ^a1 and R ^a8 have the same ^{meaning as} in the above formula. R ^a11 is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, or a trialkylsilyl group, and r is 1 to 4.

The compound having such an oxetane ring is described in detail in JP-A-2003-341217, paragraph numbers [0021] to [0084], and the compounds described herein can be suitably used in the present invention. .
Among the oxetane compounds used in the present invention, it is preferable to use a compound having one oxetane ring from the viewpoint of the viscosity and tackiness of the ink composition.

  In the ink composition of the present invention, these cationic polymerizable compounds may be used alone or in combination of two or more, but from the viewpoint of effectively suppressing shrinkage during ink curing. Is preferably a combination of at least one compound selected from oxetane compounds and epoxy compounds and a vinyl ether compound.

  The content of the cationically polymerizable compound (c) in the ink composition is suitably 10% by mass to 95% by mass, preferably 30% by mass to 90% by mass, and more preferably based on the total solid content of the ink composition. Preferably it is the range of 50 mass%-85 mass%.

  In the ink composition of the present invention, various additives can be used in combination with the essential components according to the purpose. These optional components will be described.

[(D) Colorant]
A visible image can be formed by adding a colorant to the ink composition of the present invention. For example, when forming an image area of a lithographic printing plate, it is not always necessary to add it, but it is also preferable to use a colorant from the viewpoint of plate inspection of the obtained lithographic printing plate.
There is no restriction | limiting in particular in the coloring agent which can be used here, According to a use, well-known various color materials and (pigment, dye) can be selected suitably, and can be used. For example, when forming an image excellent in weather resistance, a pigment is preferable. As the dye, both water-soluble dyes and oil-soluble dyes can be used, but oil-soluble dyes are preferred.

The pigment preferably used in the present invention will be described.
(Pigment)
The pigment is not particularly limited, and all commercially available organic and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or the resin is grafted onto the pigment surface Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A3.

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as C.I. Pigment Yellow 17; I. Non-benzidine type azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow, etc.).

  C. As a thing which exhibits red or magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

As a pigment exhibiting green, C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. And azo metal complex pigments such as CI Pigment Green 8 (Nitroso Green).
As a pigment exhibiting an orange color, C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. And anthraquinone pigments such as CI Pigment Orange 51 (dichloropyrantron orange).

Examples of the black pigment include carbon black, titanium black, and aniline black.
Specific examples of the white pigment include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), Strontium titanate (SrTiO ₃ , so-called titanium strontium white) or the like can be used.

  Here, titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

For dispersion of the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. Can do.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic polyacrylate. Carboxylic acid, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, pigment derivative and the like. It is also preferable to use a commercially available polymer dispersant such as the Solsperse series from Zeneca.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.
As a dispersion medium for various components such as pigments in the ink composition, a solvent may be added, or the above-mentioned (c) cationic polymerizable compound which is a low molecular weight component without solvent may be used as a dispersion medium. However, the ink composition of the present invention is a radiation curable ink, and is preferably solvent-free in order to cure the ink after it is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a VOC (Volatile Organic Compound) problem of the remaining solvent occurs. From such a viewpoint, as the dispersion medium, (c) a cationically polymerizable compound is used, and among them, it is possible to select a cationically polymerizable monomer having the lowest viscosity from the viewpoint of improving the dispersion suitability and the handling property of the ink composition. preferable.

The average particle size of the pigment is preferably 0.02 to 0.4 μm, more preferably 0.02 to 0.1 μm, and more preferably 0.02 to 0.07 μm.
The selection of pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so that the average particle diameter of the pigment particles is within the above-mentioned preferable range. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.
(D) When using a coloring agent, it is preferable that 1-20 mass% is added in conversion of solid content in an ink composition, and 2-10 mass% is more preferable.

(dye)
The dye used in the present invention is preferably oil-soluble. Specifically, it means that the solubility in water at 25 ° C. (the mass of the dye dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Therefore, a so-called water-insoluble oil-soluble dye is preferably used.

The oil-soluble dye preferably has a melting point of 200 ° C. or lower, more preferably has a melting point of 150 ° C. or lower, and still more preferably has a melting point of 100 ° C. or lower. By using an oil-soluble dye having a low melting point, the precipitation of dye crystals in the ink composition is suppressed, and the storage stability of the ink composition is improved.
Further, it is desirable that the oxidation potential is noble (high) in order to improve fading, particularly resistance to oxidizing substances such as ozone and curing characteristics. For this reason, as the oil-soluble dye used in the present invention, those having an oxidation potential of 1.0 V (vs SCE) or more are preferably used. The oxidation potential is preferably higher, the oxidation potential is more preferably 1.1 V (vs SCE) or more, and particularly preferably 1.15 V (vs SCE) or more.

As the yellow dye, a compound having a structure represented by the general formula (Y-I) described in JP-A No. 2004-250483 is preferable.
Particularly preferred dyes are dyes represented by general formulas (Y-II) to (Y-IV) described in paragraph [0034] of JP-A No. 2004-250483. And the compounds described in paragraph numbers [0060] to [0071] of JP-A-250483. The oil-soluble dye represented by the general formula (Y-I) described in the publication may be used not only for yellow but also for inks of any color such as black ink and red ink.

The magenta dye is preferably a compound having a structure represented by the general formulas (3) and (4) described in JP-A No. 2002-114930. Specific examples include paragraphs of JP-A No. 2002-114930. Examples include the compounds described in [0054] to [0073].
Particularly preferred dyes are azo dyes represented by the general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414, and specific examples Examples thereof include compounds described in paragraph numbers [0123] to [0132] of JP-A No. 2002-121414. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.

Examples of the cyan dye include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547, and paragraphs [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) described above are preferred, and specific examples include paragraph numbers [0052] to [0066] of JP-A No. 2001-181547. Examples thereof include the compounds described in paragraph Nos. [0079] to [0081] of Kai 2002-121414.
Particularly preferred dyes are phthalocyanine dyes represented by general formulas (CI) and (C-II) described in paragraphs [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by formula (C-II) is preferred. Specific examples thereof include the compounds described in JP-A No. 2002-121414, paragraph numbers [0198] to [0201]. The oil-soluble dyes of the formulas (I) to (IV), (IV-1) to (IV-4), (CI), and (C-II) are not only cyan but also black ink or green ink. The ink may be used for any color ink.

The dye used in the present invention preferably has an oil-solubilizing group introduced into the dye core in the various dyes listed above in order to dissolve the necessary amount in the ink composition.
As the oil-solubilizing group, long chain, branched alkyl group, long chain, branched alkoxy group, long chain, branched alkylthio group, long chain, branched alkylsulfonyl group, long chain, branched acyloxy group, long chain, branched alkoxycarbonyl group, Long chain, branched acyl group, long chain, branched acylamino group long chain, branched alkylsulfonylamino group, long chain, branched alkylaminosulfonyl group and these long chains, aryl groups containing branched substituents, aryloxy groups, aryloxycarbonyl Group, arylcarbonyloxy group, arylaminocarbonyl group, arylaminosulfonyl group, arylsulfonylamino group and the like.
In addition, for water-soluble dyes having carboxylic acid and sulfonic acid, long chain, branched alcohol, amine, phenol, aniline derivatives are used as oil-solubilizing alkoxycarbonyl groups, aryloxycarbonyl groups, alkylaminosulfonyl groups, A dye may be obtained by conversion to an arylaminosulfonyl group.

-Oxidation potential-
The oxidation potential value (Eox) of the dye in the present invention can be easily measured by those skilled in the art. Regarding this method, see, for example, P.I. Delahay, “New Instrumental Methods in Electrochemistry” (1954, published by Interscience Publishers), A.C. J. et al. "Electrochemical Methods" by Bard et al. (1980, published by John Wiley & Sons), Akira Fujishima et al., "Electrochemical Measurement Method" (published by Gihodo Publishing Co., Ltd., 1984).
Specifically, the oxidation potential is measured by placing a test sample in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate in the range of 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / Approximate the oxidization wave in a straight line by dissolving 1 liter and sweeping to the oxidation side (noble side) using carbon (GC) as the working electrode and rotating platinum electrode as the counter electrode by cyclic voltammetry and DC polarography equipment Then, the intersection of this straight line and the residual current / potential line and the intersection of the straight line and the saturation current line (or the intersection of the straight line parallel to the vertical axis passing through the peak potential value) The potential value is measured as a value relative to SCE (saturated calomel electrode). Although this value may be deviated by several tens of mil volts due to the influence of the liquid potential difference or the liquid resistance of the sample solution, the reproducibility of the potential can be ensured by inserting a standard sample (for example, hydroquinone). The supporting electrolyte and solvent to be used can be selected appropriately depending on the oxidation potential and solubility of the test sample. The supporting electrolytes and solvents that can be used are described in Akira Fujishima et al., “Electrochemical Measurement Method” (published by Gihodo Publishing Co., Ltd., 1984), pages 101-118.
(D) In the case of using a dye as a colorant, the content of the dye is preferably 1 to 20% by mass in terms of solid content in the ink composition, as in the case of the pigment, and more preferably 2 to 10% by mass. preferable.

[Other ingredients]
In addition to the components (a) to (c), which are essential components, and (d) a colorant which is optionally added to the ink composition of the present invention, various known additions used for the ink composition As long as the effect of the present invention is not impaired, the agent can be used in combination according to the purpose.

  The various additives used as necessary are described below.

(Organic acidic compound having a pKa value of 2 to 6)
In the present invention, if necessary, an organic acidic compound having a pKa value of 2 to 6 is used. An organic acidic compound having a pKa value of 2 to 6 (hereinafter also simply referred to as “organic acidic component”) corresponds qualitatively to a weakly acidic organic compound. When the pKa is in the above range, the ink composition of the present invention is preferable because of excellent sensitivity and stability over time.
Specific examples of the compound include carboxylic acids. For example, acetic acid, phenylacetic acid, phenoxyacetic acid, methoxypropionic acid, lactic acid, hexanoic acid, heptanoic acid, octanoic acid, palmitic acid, stearic acid, oleic acid, linolenic acid, cyclopropylcarboxylic acid, cyclobutanecarboxylic acid, cyclopentanecarboxylic acid Acid, cyclohexane carboxylic acid, 1-adamantane carboxylic acid, 1,3-adamantane dicarboxylic acid, norbornene-2,3-dicarboxylic acid, abietic acid, trans-retinoic acid, cyclohexyl acetic acid, dicyclohexyl acetic acid, adamantane acetic acid, malonic acid , Malonic acid monomethyl ester, fumaric acid, maleic acid, maleic acid monomethyl ester, itaconic acid, crotonic acid, succinic acid, adipic acid, sebacic acid, glycolic acid, diglycolic acid, mandelic acid, tartaric acid, malic acid, Luginic acid, cinnamic acid, methoxycinnamic acid, 3,5-dimethoxycinnamic acid, benzoic acid, salicylic acid, 4-hydroxybenzoic acid, gallic acid, 3-nitrobenzoic acid, 3-chlorobenzoic acid, 4-vinyl Benzoic acid, t-butylbenzoic acid, 1-naphthoic acid, 1-hydroxy-2-naphthoic acid, fluorenone-2-carboxylic acid, 9-anthracenecarboxylic acid, 2-anthraquinonecarboxylic acid, phthalic acid, phthalic acid monomethyl ester, Examples thereof include aliphatic or aromatic monocarboxylic acids having 1 to 20 carbon atoms such as isophthalic acid, terephthalic acid, trimellitic acid, and trimellitic acid monomethyl ester, dicarboxylic acids, and tricarboxylic acids, but the present invention is limited thereto. It is not a thing.
When an organic acidic component is used in the ink composition of the present invention, the content thereof is preferably 0.001 to 10 mass%, more preferably 0.01 to 7 mass%, based on the total solid content of the ink composition. %, More preferably 0.05 to 5% by mass. Further, when the specific base component is used, the ratio of the specific base component to the organic acidic component is preferably 0.1 to 4, and more preferably 0.8, in terms of (specific base component) / (organic acidic component) molar ratio. Used in the range of 3-2.

(UV absorber)
In the ink composition of the present invention, an ultraviolet absorber can be used from the viewpoint of improving the weather resistance of the obtained image and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194843, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492 and 56-21141 Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in No. 24239, compounds that emit ultraviolet light by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.5 to 15% by mass in terms of solid content in the ink composition.

(Sensitizer)
A sensitizer may be added to the ink composition of the present invention as necessary for the purpose of improving the acid generation efficiency of the photoacid generator and increasing the photosensitive wavelength. Any sensitizer may be used as long as the photoacid generator is sensitized by an electron transfer mechanism or an energy transfer mechanism. Preferably, aromatic polycondensed compounds such as anthracene, 9,10-dialkoxyanthracene, pyrene and perylene, aromatic ketone compounds such as acetophenone, benzophenone, thioxanthone and Michlerketone, heterocyclic compounds such as phenothiazine and N-aryloxazolidinone Is mentioned. The addition amount is appropriately selected according to the purpose, but is generally 0.01 to 1 mol%, preferably 0.1 to 0.5 mol, based on (B) the cationic polymerization initiator (photoacid generator). Used in mol%.

(Antioxidant)
An antioxidant can be added to improve the stability of the ink composition. Examples of the antioxidant include European Published Patent Nos. 223739, 309401, 309402, 310551, 310552, 457416, and German Patent No. 3435443. JP-A-54-48535, JP-A-62-262047, JP-A-63-113536, JP-A-63-163351, JP-A-2-262654, JP-A-2-71262, and JP-A-3 No. 112449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.1 to 8% by mass in terms of solid content in the ink composition.

(Anti-fading agent)
In the ink composition of the present invention, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes. No. 17643, No. VII, I to J, ibid. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in No. 15162 and the compounds included in the general formulas and compound examples of representative compounds described in JP-A-62-215272, pages 127 to 137 can be used. .
The addition amount is appropriately selected according to the purpose, but is generally about 0.1 to 8% by mass in terms of solid content in the ink composition.

(Conductive salts)
Conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride can be added to the ink composition of the present invention for the purpose of controlling ejection properties.

(solvent)
In order to improve the adhesion to the recording medium, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add the solvent within a range that does not cause the problem of solvent resistance and VOC, and the amount is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass with respect to the whole ink composition. % Range.

(Polymer compound)
Various polymer compounds can be added to the ink composition in order to adjust film properties. High molecular compounds include acrylic polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellacs, vinyl resins, acrylic resins. Rubber resins, waxes and other natural resins can be used. Two or more of these may be used in combination. Of these, vinyl copolymer obtained by copolymerization of acrylic monomers is preferred. Furthermore, as a copolymer composition of the polymer binder, a copolymer containing “carboxyl group-containing monomer”, “methacrylic acid alkyl ester”, or “acrylic acid alkyl ester” as a structural unit is also preferably used.

(Surfactant)
Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used in place of the surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.

In addition to this, if necessary, for example, leveling additives, matting agents, waxes for adjusting film physical properties, polymerization to inhibit the adhesion to recording media such as polyolefin and PET, and the like, The tackifier which does not do can be contained.
As the tackifier, specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, 5-6p (for example, (meth) acrylic acid and an alkyl group having 1 to 20 carbon atoms). An ester with an alcohol having, an ester of (meth) acrylic acid with an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer comprising an ester of (meth) acrylic acid with an aromatic alcohol having 6 to 14 carbon atoms) And low molecular weight tackifying resins having a polymerizable unsaturated bond.

  The ink composition of the present invention preferably has an ink viscosity of 7 to 30 mPa · s, more preferably 7 to 20 mPa · s at the temperature at the time of discharge in consideration of discharge properties, so that it falls within the above range. It is preferable to adjust the composition ratio appropriately. The ink viscosity at 25 to 30 ° C. is preferably 35 to 500 mPa · s, more preferably 35 to 200 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, the image quality is improved. When the ink viscosity at 25 to 30 ° C. is in the above range, the effect of preventing bleeding can be sufficiently exhibited, and the delivery of the ink liquid is favorable.

  The surface tension of the ink composition of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

The ink composition of the present invention thus prepared is suitably used not only as a general printing ink but also as an inkjet recording ink. The ink composition is printed on a recording medium by an inkjet printer, and then the printed ink composition is irradiated with radiation to be cured and recorded.
In the printed matter obtained with this ink, the image portion is cured by irradiation with radiation such as ultraviolet rays, and the strength of the image portion is excellent. Part), and can be used for various purposes.

[Inkjet recording method and inkjet recording apparatus]
Next, an ink jet recording method and an ink jet recording apparatus that can suitably use the ink composition of the present invention will be described below.

The inkjet recording method for applying the ink composition of the present invention includes (i) a step of ejecting the ink composition of the present invention onto a recording medium, and (ii) radiation to the ejected ink composition. An ink jet recording method comprising a step of curing an ink composition by irradiation.
A printed matter is obtained by forming an image with the ink composition of the present invention by the ink jet recording method.
In the ink jet recording method, it is preferable that the ink composition is heated to 40 to 80 ° C. to adjust the viscosity of the ink composition to a range of 7 to 30 mPa · s and then discharged. High discharge stability can be realized. In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, so that the viscosity fluctuation range due to temperature fluctuations during printing is large. This viscosity variation of the ink composition directly affects the droplet size and the droplet discharge speed as it is, which causes image quality deterioration. Therefore, it is necessary to keep the temperature of the ink composition during printing as constant as possible. is there. The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C.

  One feature of the ink jet recording apparatus is that it includes a means for stabilizing the temperature of the ink composition, and the portion to be kept at a constant temperature is a piping system from an ink tank (an intermediate tank if an intermediate tank is present) to the nozzle ejection surface. All of the members are targeted.

  The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. Further, the head unit to be heated is preferably thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  Next, radiation conditions will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, a light source is provided on both sides of the head unit, and the head and the light source are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed. In the present invention, these irradiation methods can be used.

  The radiation to be irradiated is not particularly limited as long as it can impart energy capable of decomposing the (b) photoacid generator, and includes active radiation including X-rays, ultraviolet rays, visible rays, and electron beams. However, ultraviolet rays having a wavelength of 230 nm to 420 nm are particularly preferable. As the light source, in addition to a polar or non-polar mercury lamp, metal halide lamp, and xenon lamp, a light emitting diode (UV-LED) in the same wavelength region can be used. When UV-LEDs are used, a plurality of LEDs are arranged in a linear or three-dimensional manner according to the energy power of the light emitting chip, and used as a multi-array.

In the present invention, the ink composition is heated to a constant temperature, and the time from landing to irradiation is desirably 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, and more preferably The irradiation is preferably performed after 0.01 to 0.15 seconds. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before curing. Also, since the ink composition can be exposed to a porous recording medium before it penetrates deeper than the light source reaches, unreacted monomer remains, and as a result, odor can be reduced. Can do.
By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. In particular, when an ink composition having an ink viscosity of 35 to 500 mP · s at 25 ° C. is used, a great effect can be obtained. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved.
In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. When inks with low lightness are stacked, it is difficult for the irradiation rays to reach the lower ink, and inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion tend to occur. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.

There is no restriction | limiting in particular as an inkjet recording device used for this invention, A commercially available inkjet recording device can be used. In other words, in the present invention, the ink composition of the present invention is applied to a recording medium by an ink jet recording apparatus, whereby recording, that is, a printed matter can be obtained.
In a printed matter having an ink image formed using the ink composition of the present invention, since the stickiness of the image surface is suppressed, even if the printed matter is laminated and stored, there is no advantage of causing a blocking. Have.

[Recording medium]
The recording medium to which the ink composition of the present invention can be applied is not particularly limited, and various non-absorbing resin materials used for ordinary non-coated paper, coated paper, and so on, so-called soft packaging, or the like. A resin film formed into a film can be used, and examples of the various plastic films include PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film. In addition, examples of the plastic that can be used as a recording medium material include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers. Metals and glasses can also be used as the recording medium.
The ink composition of the present invention has little heat shrinkage at the time of curing and excellent adhesion to the substrate (recording medium), so that the film curls and deforms due to the ink shrinkage and heat generation during the curing reaction. Films that tend to occur, such as PET film, OPS film, OPP film, ONy film, PVC film, and the like that can be shrunk by heat, have an advantage that a high-definition image can be formed.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the embodiments in these examples.
[Example 1]
<< Preparation of pigment dispersion >>
According to the method described below, yellow, magenta, cyan and black pigment dispersions 1 were prepared. The dispersion conditions are adjusted appropriately using a known dispersion device so that the average particle diameter of each pigment particle is in the range of 0.2 to 0.3 μm, and then filtered under heating. Prepared by filtration.

(Yellow pigment dispersion 1)
C. I. Pigment Yellow 12 10 parts by mass Polymer dispersing agent (Solsperse series manufactured by Zeneca) 5 parts by mass Triethylene glycol divinyl ether 85 parts by mass (magenta pigment dispersion 1)
C. I. Pigment Red 57: 1 15 parts by mass Polymer dispersing agent (Solsperse series manufactured by Zeneca) 5 parts by mass Triethylene glycol divinyl ether 80 parts by mass (cyan pigment dispersion 1)
C. I. Pigment Blue 15: 3 20 parts by mass Polymer dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Triethylene glycol divinyl ether 75 parts by mass (black pigment dispersion 1)
C. I. Pigment Black 7 20 parts by mass Polymer dispersing agent (Solsperse series manufactured by Zeneca) 5 parts by mass Triethylene glycol divinyl ether 75 parts by mass

<Preparation of ink>
The following components were mixed and filtered through a filter to prepare yellow, magenta, cyan, and black inks.

(Yellow ink 1)
-(A) Tertiary amine compound having a cationically polymerizable group (A-1) 5 g
(B) Photoacid generator:
Compound example (b-24) / (b-29) = 1/2 5 g
(C) Cationic polymerizable compound:
Celoxide 2021 (epoxy compound: manufactured by Daicel UCB) 35g
OXT-221 (Oxetane compound: manufactured by Toa Gosei Co., Ltd.) 55 g
Colorant (Pigment dispersion): Yellow pigment dispersion 15

(Magenta ink 1)
-(A) Tertiary amine compound having a cationically polymerizable group (A-1) 5 g
(B) Photoacid generator:
Compound example (b-24) / (b-29) = 1/2 5 g
(C) Cationic polymerizable compound:
Celoxide 2021 (epoxy compound: manufactured by Daicel UCB Corporation) 35 g
OXT-221 (Oxetane compound: manufactured by Toa Gosei Co., Ltd.) 55 g
Colorant (the pigment dispersion): 5 g of magenta pigment dispersion 1

(Cyan ink 1)
-(A) Tertiary amine compound having a cationically polymerizable group (A-1) 5 g
(B) Photoacid generator:
Compound example (b-24) / (b-29) = 1/2 5 g
(C) Cationic polymerizable compound:
Celoxide 2021 (epoxy compound: manufactured by Daicel UCB Corporation) 35 g
OXT-221 (Oxetane compound: manufactured by Toa Gosei Co., Ltd.) 55 g
Colorant (pigment dispersion): Cyan pigment dispersion 1 5 g

(Black ink 1)
-(A) Tertiary amine compound having a cationically polymerizable group (A-1) 5 g
(B) Photoacid generator:
Compound example (b-24) / (b-29) = 1/2 5 g
(C) Cationic polymerizable compound:
Celoxide 2021 (epoxy compound: manufactured by Daicel UCB Corporation) 35 g
OXT-221 (Oxetane compound: manufactured by Toa Gosei Co., Ltd.) 55 g
Colorant (Pigment dispersion): Black pigment dispersion 15
Sensitizer: 9,10-dibutoxyanthracene 0.5 g

<Inkjet image recording> (Evaluation of multicolor images)
Next, recording on a recording medium was performed using a commercially available inkjet recording apparatus having a piezoelectric inkjet nozzle. The ink supply system was composed of an original tank, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and heat insulation and heating were performed from the ink supply tank to the inkjet head portion. Temperature sensors were provided near the ink supply tank and the nozzles of the ink jet head, respectively, and temperature control was performed so that the nozzle portions were always 70 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that 8 to 30 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi. After landing, UV-A light is condensed to an exposure surface illuminance of 100 mW / cm ² , and the exposure system, main scanning speed, and ejection frequency are adjusted so that irradiation starts 0.1 seconds after ink landing on the recording medium. . Further, the exposure time was variable, and exposure energy was irradiated. In the present invention, dpi represents the number of dots per 2.54 cm.

Using each of the prepared color inks (yellow ink 1, magenta ink 1, cyan ink 1, black ink 1) at an ambient temperature of 25 ° C., the ink is emitted in the order of black → cyan → magenta → yellow. did. Exposure was performed with a total exposure energy per color of 300 mJ / cm ² as energy for complete curing so that tackiness disappeared by palpation. As recording media, each color image was recorded on a grained aluminum support, a transparent biaxially stretched polypropylene film having a printability, a soft vinyl chloride sheet, cast coated paper, and commercially available recycled paper. However, in both cases, a high-resolution image without dot bleeding was obtained. Furthermore, even on high-quality paper, the ink was sufficiently cured without causing the ink to turn around, and there was almost no odor due to unreacted monomers. Further, the ink recorded on the film had sufficient flexibility, the ink did not crack even when it was bent, and no stickiness of the surface due to finger touch was observed. Regarding image adhesion, there was no problem in the adhesion test by peeling the cellophane tape.

[Examples 2 to 10, Comparative Examples 1 and 2]
<Preparation of ink>
The magenta ink compositions of Examples 2 to 10 (magenta inks 2 to 2) were the same as magenta ink 1 of Example 1, except that the components used for magenta ink 1 in Example 1 were changed to the following components. 10) was prepared.
The ink composition of Comparative Example 1 (magenta ink 11) was prepared in the same manner as in Example 10 except that the ink composition of Example 10 did not contain (a) a tertiary amine compound having a cationic polymerizable group. Obtained. (A) Comparative Example 2 was carried out in the same manner as in Example 10 except that Comparative Compound 1 (1,2,2,6,6-pentamethylpiperidine) was added as a tertiary amine compound in place of the polymerizable amine compound. Ink composition (magenta ink 12) was obtained.

(Magenta ink 2-10)
(A) Tertiary amine compound having a cationic polymerizable group (compound described in Table 1) 5 g
(B) Photoacid generator (compound described in Table 1) 8 g
(C) Cationic polymerizable compound 87 g
(D) Colorant (magenta pigment dispersion 1) 5 g

In addition, the detail of the cationically polymerizable monomer of Table 1 is as follows.
Cationic polymerizable compound 1:
Celoxide 2021 (epoxy: manufactured by Daicel UCB) / OXT-221 (oxetane: manufactured by Toagosei Co., Ltd.) = 35/55 mixture Cationic polymerizable compound 2:
Celoxide 3000 (epoxy: manufactured by Daicel UCB Co., Ltd.) / OXT-211 (oxetane: manufactured by Toagosei Co., Ltd.) = 50/40 mixture

  In the ink compositions prepared in the above examples and comparative examples, the ink viscosity at the ejection temperature was in the range of 7 to 20 mPa · s.

[Inkjet image recording] (single color image evaluation)
Using the magenta inks 2 to 12 (Examples 2 to 10, Comparative Examples 1 and 2) prepared as described above and the magenta ink 1 prepared in Example 1, the same manner as that described in Example 1 was used. A magenta image was printed.

1. Measurement of curing sensitivity Exposure energy (mJ / cm ² ) that eliminates stickiness on the image surface after UV irradiation
Was defined as curing sensitivity. The smaller the value, the higher the sensitivity.

2. Storage stability evaluation After the ink composition was stored at 75% RH and 60 ° C. for 3 days, the ink viscosity at the injection temperature was measured, and the increase in the ink viscosity was calculated as the viscosity ratio after storage / before storage. expressed. If the viscosity does not change and is close to 1.0, the storage stability is good, and if it exceeds 1.5, clogging may occur at the time of injection, which is not preferable.

3. Permeability evaluation with respect to commercially available recycled paper For images printed on commercially available recycled paper, the permeability was evaluated according to the following criteria.
○: Almost no penetration and residual monomer odor is not recognized.
△: Slightly penetrated and a slight residual monomer odor X: Clearly the ink penetrated to the back side and the residual monomer odor was strong.

4). Ink bleed evaluation on a PVC substrate An image printed on a surface-treated PVC substrate was evaluated for ink bleed according to the following criteria.
○: No blur between adjacent dots Δ: Slightly blur dots ×: Dot blurs and the image is clearly blurred

5). Evaluation of adhesion on PVC substrate For the printed image created above, in accordance with JISK 5400, a sample that does not scratch the printed surface at all, and on the printed surface, 11 cuts are made vertically and horizontally at intervals of 1 mm, Prepare 100 samples of 1 mm square grids, apply cellophane tape on each print surface, quickly peel off at an angle of 90 degrees, and the remaining print image or grid pattern remains as follows. Evaluation was made according to the criteria.
○: No peeling of the printed image by the cross cut test is observed. Δ: Some peeling of the ink is recognized by the cross cut test, but almost no peeling is observed unless the ink surface is scratched. Easy to peel off with cellophane tape

6). Measurement of blocking property In order to evaluate the blocking property with the back side of the base material when it is stored repeatedly, 50 sheets of A4 size printed base material are stacked, a 6 kg weight is placed on top, and printed after 24 hours at room temperature. The substrate was peeled off, and the adhesion between the ink image and the adjacent substrate was evaluated according to the following criteria.
○: The ink image is sufficiently cured, and adhesion with an adjacent substrate is not recognized.
Δ: There is a slight stickiness on the surface of the ink image, and there is a sound when peeling off.
X: The ink image surface adheres to the adjacent substrate and does not peel off.
The results of these performance evaluations are shown in Table 1 below.

From the results shown in Table 1, the ink composition of the present invention containing (a) a tertiary amine compound having a cationically polymerizable group is compatible with storage stability and sensitivity, and has good adhesion to a PVC substrate with good bleeding. A high-quality image with no image could be formed. It was also found that the stickiness of the ink image surface was suppressed and the sensitivity to blocking was greatly improved.
On the other hand, the ink composition of Comparative Example 1 in which (a) the polymerizable amine compound was not added had a problem in storage stability because the viscosity of the ink was significantly increased. (A) In Comparative Example 2 in which Comparative Compound 1 (1,2,2,6,6-pentamethylpiperidine), which is an amine compound having no polymerizable group, was added in place of the polymerizable amine compound, sensitivity and storage were obtained. Although the stability was improved, the ink image surface was sticky and the blocking property was deteriorated.

Claims (6)

  An ink composition comprising (a) a tertiary amine compound having a cationic polymerizable group, (b) a photoacid generator, and (c) a cationic polymerizable compound.   The ink composition according to claim 1, wherein the tertiary amine structure in the tertiary amine compound (a) having a cationic polymerizable group is a hindered amine structure.   3. The ink composition according to claim 1, wherein the tertiary amine compound (a) having a cationically polymerizable group has a vinyl ether group.   The ink composition according to claim 1 or 2, wherein the (a) tertiary amine compound having a cationically polymerizable group has an epoxy group or an oxetane group.   The ink composition according to any one of claims 1 to 4, further comprising (d) a colorant.   The ink composition according to any one of claims 1 to 5, which is used for inkjet.